Sahih Bukhari Volume 8, Book 78, Hadith Number 696.

Narated By ‘Abdullah bin ‘Umar : That he was asked about a man who had vowed that he would fast all the days of his life then the day of ‘Id al Adha or ‘Id-al-Fitr came. ‘Abdullah bin ‘Umar said: You have indeed a good example in Allah’s Apostle. He did not fast on the day of ‘Id al Adha or the day of ‘Id-al-Fitr, and we do not intend fasting on these two days.